net: reintroduce missing rcu_assign_pointer() calls

commit a9b3cd7f32 (rcu: convert uses of rcu_assign_pointer(x, NULL) to
RCU_INIT_POINTER) did a lot of incorrect changes, since it did a
complete conversion of rcu_assign_pointer(x, y) to RCU_INIT_POINTER(x,
y).

We miss needed barriers, even on x86, when y is not NULL.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
CC: Stephen Hemminger <shemminger@vyatta.com>
CC: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index abf4393..f3dbd4f 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -1177,9 +1177,9 @@
 			nonempty = 1;
 	}
 
-	if (nonempty)
-		RCU_INIT_POINTER(dev->xps_maps, new_dev_maps);
-	else {
+	if (nonempty) {
+		rcu_assign_pointer(dev->xps_maps, new_dev_maps);
+	} else {
 		kfree(new_dev_maps);
 		RCU_INIT_POINTER(dev->xps_maps, NULL);
 	}